Mandrel for mechanically converged electron gun



Nov. 24, 1959 L. D; MILLER ETAL 2,914,317

' MANDREL FOR MECHANICALLY CONVERGED ELECTRON GUN Filed Jan. 21, 1954 1a" f, v i 12 l fl INVENTORS laws 0 Mam? 4M0 Howma K. Mega/um United States Patent O 'ice MANDREL FOR MECHANICALLY CONVERGED ELECTRON GUN LouisD :Miller, Akron, and Howard R. McQuillen, Lancaster, Pa., assignors to Radio Corporation of Americma corporation of Delaware Application January 21, 1954, Serial No. 405,434

7 7 Claims. (Cl. 269117) This' invention relates to the assembly of multiple electron gun' cathode ray tubes and particularly to a mandrel for assembling mechanically converged multiple electron guns for a cathode ray tube.

When using the present-day manufacturing techniques, the three individual electron guns of a cathode ray tube are each assembled as a separate sub-assembly before these individual guns are connected together to form the ultimate multiple electron gun assembly. One method of assembling the individual guns is described and claimed in a patent .to R. R. Law which was issued December 23, 1941, Patent Number 2,266,773. This patent describes a method of assembling a single electron gun by supporting the various electrodes included within the electron gun in the desired relationship by means of glass beads sealed to studs extending from the various electrode elements.

' An assembly of three electron guns is used in one type of television picture for the reproduction of an image in color. In this tube, the three guns are mechanically mounted so that their axes converge at a common point substantially at the phosphor screen assembly. When utilizing mechanically converged electron guns, it is necessary to provide some type of jigging means for the composite assembly of the three electron guns from the converged end of the assembly due to the fact that the cathodes obstruct internal jigging from the diverged end of the assembly. .When providing a jigging means from the converged'end of the assembly, some means must be provided to remove the jig from the assembled mount without destroying the relationship existing between the individual electron guns of the assembled mount.

If mechanical convergence is not utilized for the three individual guns, a large amount of magnetic or electrostatic convergence must be provided in order to converge the three electron beams at the proper point. When mechanical convergence is utilized, some accurate jigging in present-day mass production techniques.

' It is, therefciregan object of this invention to provide a new and-improved method of and means for assembling the electron guns of a'cathode ray tube.

1" .It is another object ofthis invention to provide a new and novel mandr'el'which is adapted for use in the assembly of the electron guns of a cathode ray tube.

It is a further object of this invention to provide a new and novel mandrel on which the electron guns of a cathode ray tube may beassembled accurately, and with 'f ease, and, which may be quickly removed from the assembled structure.

""It is a still further object of this invention to provide a ,newa'nd improved method of assembling a mechanically converged electron gun mount.

These and other objects are accomplished in accordance 2,914,317 Patented Nov. 24,- 1959 rate electron guns in accurate converged alignment and from the converged end thereof. The mandrel for the electron guns is utilized while the three guns are being mechanically connected together, and is easily removed after the assembly has been completed without disturbing the relationship of the three mechanically converged electron guns.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself will best be understood by reference to the following description taken in connection with the accompanying single sheet of drawings in which:

Figure 1 is a top plan view of a mandrel in accordance with this invention;

Figure 2 is a sectional view of the mandrel shown in Figure 1 taken along line 2-2 of Figure 1;

Figure 3 isa sectional view of a mandrel in accordance with-this invention taken along line 33 of Figure 4 and showing a unit assembled on the mandrel; and

Figure .4 is an elevational view partially in section of a mandrel in accordance with this invention and showing a unit assembled on the mandrel.

Referring specifically now to Figures 1 and 2, there is shown a mandrel 10 in accordance with this invention. The mandrel 10 comprises a base member 12 having an alignment pin 14 located therein. The alignment pin 14 properly orients a hollow cylindrical clamp member 16 on the base 12. Supported on the base 12, and partially extending within the clamp 16, is a V-block 18 .which has three V-shaped pin-receiving sections 17 there- 'in (shown more clearly in Figure 1).

The V-block 18, which is machined so as to fit into clamp 16, slides into the clamp 16 and is supported in a tight relationship with respect to the base member 12 by means of tighteningscrews 20 extending through the base 12. Each section of the V-block 18 includes an alignment pin 22 which serves to align a portion of the gun structure as will be means which are represented by screws 24. Fitting into the pin-receiving sections of the V-block 18 are three mandrel 'pins 26. Each of these mandrel pins includes a tapered end 26, and a neck portion 26". The tapered end 26' of each of the pins 26 is tapered forty-nine minutes, has a length of 1.507 inches and a radius at the larger end of .0033 inch, for the particular gun structure under consideration herein.

When the mandrel pins 26 are inserted in the V-block 18 and the screws 24 are tightened, the mandrel pins 26 are pressed against the vertical sides of the V-block 18 which automatically results in an angular displacement from the axis of base member 12 of 1 degree 10 minutes on each of the mandrel pins. The displacement of the mandrel pins 26 of 1 degree 10 minutes from the axis results fromthe fact that, even though the taper on the tapered ends 26' of mandrel pins 26 is only forty-nine minutes, the tapered ends 26 are smaller in the area adjacent to the flat plane of base 12 and thus fit deeper into the Vs of theV-blocks 18 resulting in a larger angular displacement than the forty-nine minutes. The particular taper for each of the mandrel pins will depend upon the specific tube size for which the mandrel is designed.

It is important that the rounded bottomend of the mandrel pins 26 rest on the fiat plane of the base 12. The distance from the flat plane of base 12 to the position ofsupport disk 44 (Fig. 4), in combination with the radial spacing of the Vs in V-block 18, is calculated to result in the correct spacing from the axis of 1 degree minutes for the electron guns 30 at the support disk 44, in order to obtain the correct spacing of the electron beams from guns 30. The ends of the tapered end 26' of the mandrel pins 26 should have a radius of approximately 30 degrees to insure that the ends will not wear down from use which would change the spacings of the electron guns 30. The dimensions given are for a 19-inch cathode ray tube. Each of the parts of mandrel 10 may be made of a suitable metal, such as a high-grade stainless steel, and is preferably accurately machined within close angular tolerances by standard machine shop techniques.

Referring now to Figures 3 and 4, there is shown a mandrel 10 in the process of being utilized to assemble three separate electron guns 30. Each of the guns 30 comprises a cathode 32, a control grid 34, a first accelcrating grid 36, a second accelerating grid 38,a'nd a focusing electrode 40. The various elements of each of the guns 30 are joined in a predetermined spaced relationship with each other, and are held in this relationship by means of beads 42. The structure of electron guns 30,, and their operation, is explained more completely in a copending application of A. M. Morrell, filed September 30, 1953, Serial Number 383,340, now U.S. Patent 2,847,600, and assigned to the same assignee as the present invention. The sub assembly of the separate electron guns 30 may be constructed by the method taught in U.S. Patent 2,266,773.

The mandrel 10 is utilized to assemble an electron gun mount in accordance with this invention as follows: First, a disk 44, for supporting the focusing electrode 40, is placed on the V-block 18 and is aligned with the apertures therein by means of the three alignment pins 22 extending from the top of V-block 18 into similarly located apertures in the disk 44. The three mandrel pins 26 are now inserted through apertures in disk 44 into the pin-receiving area 17 of V-block 18 and the screws 24 are tightened. The tightening of screws 24 automatically provides the desired taper of 1 degree 10 minutes on each of the mandrel pins 26. Each connection member 50 is then placed in position on the disk 44. Each of the individual gun Sub-assemblies 30 are now placed on the mandrel pins 26. As may be seen from Figure 4, the body portion of mandrel pins 26 extends to the apertured baffie 45 in the second accelerating electrode 38, while the neck portion 26" of mandrel 26 extends to the space enclosed by the first accelerating electrode 36. Of course, other lengths of mandrel pins 26 are within the contemplation of this invention. However, it has been determined that mandrel pins similar to those shown and described herein result in a mechanically stable, extremely accurately aligned three electron gun assembly.

When the separate electron gun assemblies 30 are fitted onto the mandrel pins 26, there is inserted between the three electron guns 30 a substantially triangular supporting disk 46 (shown better in Figure 3) which is mechanically conencted to each of the ring elements 48. The ring elements 48 have previously been connected, such as by welding, to each of the second accelerating electrodes 38 of the electron guns 30. The mechanical connection of the supporting disk 46 to the ring elements 48, as well as the mechanical connection of the ring elements 48 to the second accelerating electrodes 38, may be accomplished by any of the well-known methods of securing metals, such as by spot welding.

The exposed end of each of the focusing electrodes 40, of each of the individual guns 30, is mechanically connected to the disk 44 by being welded to connection members 50 which are in turn welded to each of the fourth accelerating electrodes 40. At this time, a separate lathe ,(not shown) may be utilized to apply a glass st t the structure and the individual lead connections may be connected to the separate electrode elements of the guns 30.

When the proper supporting welds have been made, the screws 24 are loosened and the mandrel base member 12, clamp 16, and V-block 18 are removed from the assembled structure. Due to the fact that the mandrel securing screws 24 have been loosened, and due to the parallel walls of the pin-receiving areas 17 of V-block 18, the base member 12 along withthe cylindrical clamp 16 and the V-block 18 may be removed from the assembled three gun structure without producing any forces which would tend to disturb the accurate relationship of the three gu 3 W en t i do e. the man rel. Pin 26 remain in the assembled structure of the electron guns. When this has been done, the separate mandrel pins 26 are removed individually so that proper clearance between the separate pins 26 is obtained.

For gun assemblies that are designed for tubes other than the specific example disclosed, the angle of the mandrel pins 26 should be changed. For tubes having small angles of tilt on the electron guns, i .e., those adapted for use in cathode ray tubes having'a face plate larger than 12 inches, the tangent of the angle of tilt for each of the guns 30 is approximately equal to the /2 times the tangent of the taper angle of the mandrel pins 26.

What is claimed is:

1. A mandrel for the assembly of a mechanically converged electron gun mount comprising a base member, a hollow cylindrical clamp member supported by said base member, a V-block member suported on said base member and extending into said clamp member, said V-block member and said clamp member forming a plurality of pin-receiving areas with the walls of said pin-receiving areas being substantially parallel to the axis of said man'- drel, a plurality of mandrel pins each having a tapered end removably mounted in one of said pin-receiving. areas, pin-securing means extending through the walls or said clamp to press each of said mandrel pins against said V-block whereby said mandrel pins are secured at a predetermined angle with respect to the axis of said mandrel.

2. A mandrel as in claim 1 wherein said predetermined angle is 1 degree 10 minutes.

3. A mandrel as in claim 1 wherein said taper on said mandrel pins is a taper of 49 minutes. i

4. A mandrel as in claim 1 wherein said pimsccuring means is capable of being loosened whereby said base member, said clamp, and said V-hlock may be removed from said mandrel pins without disturbing said predetermined angle. A

5. A mandrel for the assembly of a mechanically converged electron gun mount comprising a hollow cylindrical clamp member, a V-block member extending into said clamp member and forming therewith a plurality of pin-receiving areas, the sides of said pin-receiving areas being substantially parallel to a common axis, a plurality of mandrel pins each having a tapered end in one of said pin-receiving areas, and pin-securing means extending through the walls of said clamp members for pressing each of said mandrel pins against a parallel surface of said V-block whereby said pins are supported at a predetermined angle with respect to the walls of said V.-block.

6. A mandrel assembly comprising a support means, a plurality of elongated mandrel pins, each of said pins being tapered adjacent to one end and being cylindrical adjacent to the other end, the taper on each of said pins being substantially the same, said support means including a common planar supporting surface for supporting said one end of said pins, said supporting meansjurther including a plurality of parallel walls arranged perpendicular to said supporting surface and parallel to and q a eed f m. and. ra ial d sp sed about a 9 n a is e n in t r h a d upi t ps whe ar tapered portion of said pins detachahly. engaging walls, and securing means for locking said pin's' inposi- 5 6 tion by forcing the tapered portion of said pins against 799,026 Barrow Sept. 12, 1905 said walls. 1,481,212 Keller Jan. 15, 1924 7. A mandrel as in claim 6 wherein said taper on said 2,433,339 Brown Dec. 30, 1947 mandrel pins is a taper of 49 minutes. 2,459,080 Willius J an. 11, 1949 5 2,721,374 Pilas Oct. 25, 1955 References Cited in the file of this patent UNITED STATES PATENTS Re. 22,378 Bowie Sept. 21, 1943 

